1. Field of the Invention
The present invention relates to a single plate color projection type display apparatus which uses a single liquid crystal light valve, more particularly to a projection apparatus which irradiates respective R, G and B light beams from different directions onto its single liquid crystal light valve and projects modulated light beams of the respective R, G and B light beams emitted from the light valve to perform full color display.
2. Descriptions of the Related Arts
A projection type display apparatus proposed in Japanese Patent Laid Open No. 4-60538 has been known, which allows R, G and B light beams to be incident onto a single liquid crystal light valve from different directions and composes modulated light beams of the respective R. G and B light beams emitted from the light valve to project the composed light.
This conventional projection type display apparatus will be described with reference to FIGS. 11 and 12. FIG. 11 is a schematic diagram showing a constitution of the conventional projection type display apparatus. FIG. 12 is a schematic section view showing a light valve of the display apparatus shown in FIG. 11.
In this conventional projection type display apparatus, a source light emitted from a light source, which is constituted by the lamp 101 and the spherical mirror 102 disposed on the rear surface of the lamp 101, is shaped into approximately a parallel light beam by the shaping lens 103. This parallel light beam is incident onto a color separation optical system composed of the R light reflection dichroic mirror 104R, the G light reflection dichroic mirror 14G and the B light reflection dichroic mirror 104B which are disposed on the optical axis so that incidence angle of the light beam relative to the dichroic mirror 104R is about 45 degrees. The dichroic mirrors 104R, 104G and 104B are disposed so that they are perpendicular to the paper plane and form predetermined angles of several degrees with each other. The arrangement causes the R light reflected by the R light reflection dichroic mirror 104R, the G light reflected by the G light reflection dichroic mirror 104G and the B light reflected by the B light reflection dichroic mirror 104B to be incident onto the light valve composed of the liquid crystal display panel 120 and the micro lens array 110 additionally provided in the panel 120, while forming different angles relative to them.
As shown in FIG. 12, the liquid crystal display panel 120 has a structure in which the liquid crystal 123 is sealed between the two transparent glass substrates 124 and 125. The liquid crystal 123 is sandwiched, for example, between the counter electrode 122 formed of an ITO film and pixel electrodes 121R, 121G, and 121B formed of an ITO film arranged like a matrix, and controlled in response to the electric field between these electrodes. Each of the pixel electrodes 121R, 121G, and 121B is, although not shown in FIG. 12, electrically connected to the scan line and the signal line though the thin film transistor. It should be noted that in FIG. 12, a polarization plate and an orientation film are omitted, which are components of the liquid crystal display panel 120.
As described above, the R, G and B light beams incident onto the micro lenses of the micro lens array 110 are caused to be incident collectively onto color pixels, while forming the predetermined different angles as shown in FIGS. 11 and 12. Each of the R, G and B light beams incident onto the color pixel is modulated in the corresponding pixel by the pixel signal, so that each light exits outward. Each light passes through the field lens 105 and is projected onto the screen 107 by the projection lens 106, so that an image in full color is displayed. It should be noted that in the liquid crystal panel 120, a non-linear switching element such as TFT and MIM is disposed for each pixel of the liquid crystal light valve and the switching element is selectively switched, thereby modulating each color light beam by the foregoing signal.
In recent years, for the projection type display apparatus, enlargement of the screen for its projection image has progressed. However, with the enlargement of the screen, brightness of the projection image projected by the foregoing conventional projection type display apparatus is not satisfactory and luminance with a higher brightness has been demanded.
In order to achieve a higher luminance for the conventional projection type display apparatus, a lamp exhibiting a high power, which is used for the light source, may be employed. In this case, other problems such as an establishment of a cooling method to cope with the heat generation of the light source newly arise, which must be solved.